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I'm quite interested to know what drop in exists, because I've seen only R-22a for sale as a replacement. From what I can find, and I don't trust everything on the internet, R-22a is R-290 (propane).

This is from wiki.answers.com --

"In the USA it is unlawful to mix R-22 (chlorodifluoromethane) with R-22a aka R-290 (propane, aka liquiefied petroleum gas) (propane). While the two are not incompatible working fluids mixing them is a bad idea even where it is not unlawful. R-290 is a known refrigerant with many excellent properties and one major drawback - flammability. As a practical matter, R-22 was created because early air conditioners using ammonia, propane, and other toxic or flammable materials were dangerous when they failed, and air conditioning was not accepted as safe for the home. Propane has not become any less flammable since that time. In the event of a rapid loss of refrigerant (e.g. compressor terminal blowout) an electrical spark (from the live wire on the terminal blown out) may ignite it. In such an event any R-22 also present would decompose into highly toxic fumes greatly increasing the risk of accidental death. As a further caution to tinkerers, commonly available LPG propane (but not R-22a or R-290) has a sulfur compound (a mercaptin) added for leak detection that would have an undesirable effect on the lubrication oil in a sealed system."

"We are what we repeatedly do, excellence then is not an act, but a habit." -Aristotle

There are NO refrigerants that can be mixed with 22... ALL replacement must follow a procedure of reclaim, N2 flush, some change the oil--RX11 flush also, some change some seals, evacuate, charge with different refrigerant.
Most all will have a minor capacity reduction... ranging from 7-8% to 15-20%.

"Although EPA does not recognize any refrigerants as being "drop-in" substitutes, in general usage of the term means that the refrigerant provides exactly the same cooling, efficiency, durability, and other performance factors as the original refrigerant, with no changes to existing equipment. For purposes of SNAP determinations, EPA does not distinguish between drop-in and retrofit substitutes. The retrofit designation identifies substitutes that may be used in systems retaining at least some of the original equipment. Retrofits will generally be less expensive than new systems, meaning total replacements. Many substitutes will be acceptable in both categories. Alternative technologies will usually be deemed acceptable only in new equipment, since they cannot utilize parts of existing systems."

So you're on your own, or you must rely on promises from the manufacturers who package blended and sometimes flammable replacement refrigerants... the EPA SNAP program will not provide solutions or recommendations. However, I found an interesting article by Rajan Rajendran of Emerson Climate Technologies in Sidney, OH. (see attachment)RefrigerantUpdates.pdf

Originally Posted by HvacBry

I asked a question similar to this last friday in EPA class at school. Asked if there was a R22 drop in replacement available that would be available due to the phase-out.

I was told that as far as the EPA was concerned there was no drop in or replacement.

i dont know if my reply here helps or hinders, but figured i would pass that little tidbit along. Hope this helps.

"We are what we repeatedly do, excellence then is not an act, but a habit." -Aristotle

"Alternatives to R-22 in Residential Air Conditioning
As R-22 is gradually phased out, non-ozone-depleting alternative refrigerants are being introduced. Under the Clean Air Act, EPA reviews alternatives to ozone-depleting substances to evaluate their effects on human health and the environment. EPA has reviewed several alternatives to R-22 for household and light commercial air conditioning and has compiled a list of substitutes that EPA has determined are acceptable. One of these substitutes is R-410A, a blend of hydrofluorocarbons (HFCs) that does not contribute to depletion of the ozone layer, but, like R-22, contributes to global warming. R-410A is manufactured and sold under various trade names, including GENETRON AZ-20®, SUVA 410A®, Forane® 410A, and Puron®. An additional refrigerant on the list of acceptable substitutes for R-22 in residential air conditioners and other products is R-407C. Residential air conditioners and heat pumps using R-407C are not available in the U.S., but are commonly found in Europe. EPA will continue to review new non-ozone-depleting refrigerants as they are developed."

Those last two sentences seem slightly contradictory, either R-407C is a substitute or it is not.

Originally Posted by ga-hvac-tech

Do some searching... there is a recent thread at H-talk about this.

R-407C is approved for some dry units... MO99 is a candidate.

There are NO refrigerants that can be mixed with 22... ALL replacement must follow a procedure of reclaim, N2 flush, some change the oil--RX11 flush also, some change some seals, evacuate, charge with different refrigerant.
Most all will have a minor capacity reduction... ranging from 7-8% to 15-20%.

"We are what we repeatedly do, excellence then is not an act, but a habit." -Aristotle

One thing that should be looked for and considered with replacement refrigerants of R22, is the oil and capacity losses. some of the replacement refrigerants you may have to mix oils or add more carbons to the oil which alter the composition of the oil and how it works with the refrigerant. Then there is possibly capacity losses with the replacement refrigerant. Also there is part replacement i.e pressure switches, and maybe with some replacement refrigerants the metering device may need to be replaced. Also the compressor may need to be up sized to compensate for capacity losses for low temp refrigeration equipment. I believe this is the governments way of forcing people to make this "switch" weather it is replacing the refrigerant and components or buy new equipment..

R-410A is a wholly different class of refrigerant... it operates at pressures something like 60-70% higher than R-22.

OTOH: R-407C (which is used in refrigeration) is compatible (more or less) with most R-22 equipment. Note that some Rheem cube variants (different names on the same equipment), and some Nordyne units... ALL dry charge units... are approved by the manufacturer to use R-407C.

MO99 is another variant... it works well with mineral oil (hence the MO)... and is close enough to R-22 you do not need to change the TXV bulb and can use P/T charts for R-22.

What the EPA says... and what the industry does... are two things. Each person decides what their co will supply to market needs... and does it.

"Alternatives to R-22 in Residential Air Conditioning
Residential air conditioners and heat pumps using R-407C are not available in the U.S., but are commonly found in Europe. EPA will continue to review new non-ozone-depleting refrigerants as they are developed."

Those last two sentences seem slightly contradictory, either R-407C is a substitute or it is not.

R-407C was a common replacement in some air cooled chillers from 2005 ish till around 2009. It is not a drop-in by any stretch of the imagination, it is a replacement. Meaning that it exhibits a similar pressure and temperature glide and can be used in place of R-22 by the manufacturers. No residential manufacturer to my knowledge, ever submitted any equipment using 407 for approval. Pretty much everyone made the move to R-410A. Even on the heavy commercial/industrial level, we are seeing R-410A on the vast majority of mid temp equipment. Process cooling is a different story, but that is another argument all together.

R-407C was a common replacement in some air cooled chillers from 2005 ish till around 2009. It is not a drop-in by any stretch of the imagination, it is a replacement. Meaning that it exhibits a similar pressure and temperature glide and can be used in place of R-22 by the manufacturers. No residential manufacturer to my knowledge, ever submitted any equipment using 407 for approval. Pretty much everyone made the move to R-410A. Even on the heavy commercial/industrial level, we are seeing R-410A on the vast majority of mid temp equipment. Process cooling is a different story, but that is another argument all together.

The Rheem cube has approved AHRI matches for R407C ... They are the only ones that I have found ... tht is not saying that Nordyne may as well ..

R-407C was a common replacement in some air cooled chillers from 2005 ish till around 2009. It is not a drop-in by any stretch of the imagination, it is a replacement. Meaning that it exhibits a similar pressure and temperature glide and can be used in place of R-22 by the manufacturers. No residential manufacturer to my knowledge, ever submitted any equipment using 407 for approval. Pretty much everyone made the move to R-410A. Even on the heavy commercial/industrial level, we are seeing R-410A on the vast majority of mid temp equipment. Process cooling is a different story, but that is another argument all together.

IMO the highlited sentence above is the key. There are NO 'drop in' refrigerants for R-22... only replacements.

If we follow the procedures of changing a refrigerant... and change it to something that is similar in performance characteristics as what we are replacing... well that can and sometimes will... work. 'WORK' being a word with a variable definition.

Personally, as someone that does mostly residential work... Just sell them a new 410 system...

IMO the highlited sentence above is the key. There are NO 'drop in' refrigerants for R-22... only replacements.

If we follow the procedures of changing a refrigerant... and change it to something that is similar in performance characteristics as what we are replacing... well that can and sometimes will... work. 'WORK' being a word with a variable definition.

Personally, as someone that does mostly residential work... Just sell them a new 410 system...

+1, if you are replacing the condesner, replace the indoor coil also...